Preparation of cyanopyridines

ABSTRACT

Cyanopyridines are prepared by bringing a reactant stream comprising an alkyl substituted pyridine, ammonia, steam and oxygen into contact with a novel catalyst composition which results in high selectivity to the desired cyanopyridine.

This invention relates to chemical compositions and a process for theproduction of cyanopyridines from alkyl substituted pyridines.

One of the problems inherent in an ammoxidation system and particularlyin a system employing excess oxygen in the reactant stream isundesirable combustion of organic reactant and ammonia to unwantedby-products rather than nitrile products. This, of course, adds toprocess costs in that more reagent is required to produce a given amountof nitrile (e.g., yields are reduced) and also larger capital investmentis required to build a plant for a given capacity. Obviously then, areduction in the undesired combustion of ammonia and organic reactantwith the attendant yield increase is a desirable objective.

It has now been found that in the vapor phase ammoxidation of alkylsubstituted pyridines the yield of desired cyanopyridine can besignificantly increased and ammonia and hydrocarbon decompositionmitigated, and this is accomplished in accord with this invention byutilizing the inventive catalyst compositions in a fixed bed catalystsystem.

An advantage of the present invention is that the catalyst does not haveto be periodically regenerated and still the high selectivity to thedesired cyanopyridine remains. Another advantage is that an adiabatic orisothermal type reactor can be utilized which results in allowance oftemperature fluctuations without any significant decrease in the highselectivity to the desired cyanopyridine by utilizing the catalystcompositions of the present invention. Also, low molar ratio of ammoniaand oxygen to the alkyl substituted pyridine can be utilized whichresults in lower amounts of undesirable side products.

An important aspect of the present invention is the high selectivity tothe desired cyanopyridine. That is, of the alkyl substituted pyridinethat is converted into products by coming into contact with thecatalyst, a higher percentage is converted to the desired3-cyanopyridine than is shown in the prior art.

Thus, according to the invention, there is described a process for theproduction of cyanopyridines from alkyl pyridines which comprisespassing as a reactant stream a gaseous mixture comprising:

1. AN ALKYL SUBSTITUTED PYRIDINE;

2. AMMONIA;

3. STEAM; AND

4. OXYGEN

Wherein the mole ratios of said reactants are:

AMMONIA:ALKYL PYRIDINE, 1:1 TO 10:1;

STEAM:ALKYL PYRIDINE, 0.01:1 TO 10:1;

OXYGEN:ALKYL PYRIDINE, 2:1 TO 50:1

The improvement being passing said reactant stream over a fixed bedammoxidation catalyst at a temperature of about 280°C. to 400°C. andwherein said catalyst consists essentially of (V₂ O₅ +MoO₃ +P₂ O₅+SnO₂)/pumice in a molar ratio of 2.5:1.0:0.015:3.5.

The catalyst composition utilized in carrying out the process of thepresent invention is a novel and useful composition. The precise molarratios of the catalyst components account for the unusual and novelresults.

The novel composition consists of vanadium pentoxide (V₂ O₅), molybdenumoxide (MoO₃), phosphorus pentoxide (P₂ O₅) and stannic oxide (SnO₂) onpumice stone wherein the molar ratios of V₂ O₅ :MoO₃ :P₂ O₅ :SnO₂ are2.5:1.0:0.015:3.5.

In carrying out the process of the invention, the reactor and attendantequipment is prepared in the usual way, the reactor being charged withcatalyst and otherwise prepared for startup including the conditioningof catalyst, if desired. The alkyl substituted pyridine, ammonia, steamand oxygen stream are then passed over the catalyst at reactionconditions at certain mole percent ratios. Preferred reactiontemperature is about 330°C. to about 390°C. at essentially atmosphericpressure.

By the term, "high selectivity" is meant that the amount of alkylpyridine converted to the cyanopyridine is greater than 70%.

Typical alkyl substituted pyridines suitable for conversion intocyanopyridines according to this invention are 2-, 3- and 4-picolines;the 2,3-, 2,4-, 2,5-, 2,6- and 3,4-dimethyl pyridines; the 2,3,4-,2,4,6-, 2,3,6- and 2,3,5-trimethyl pyridines; the 2-, 3- and 4-ethylpyridines; 2-methyl-5-ethyl pyridine, and 2-ethyl-5-methyl pyridine.

The catalyst support suitable for this invention is specific in order toachieve the catalyst activity and catalyst selectivity to the desiredproduct. In this particular invention, the catalyst support is pumice.

The weight percent loading of the catalyst on the support can vary fromabout 5 to 50%. A more preferred weight percent utilized in the practiceof this invention is from about 40 to 50%.

EXAMPLE 1 Preparation of catalyst (V₂ O₅ +MoO₃ +P₂ O₅ +SnO₂)/pumice

The catalysts utilized in the practice of this invention are novelcompositions. These compositions are responsible for the high degree ofselectivity in the conversion of reactants to the desiredcyanopyridines. An illustration of the preparation of these catlystcompositions is as follows: 38.9 gm. of vanadium pentoxide (V₂ O₅powder) is added to 120 ml. of water and heated to 90°C. To this mixtureis slowly added 130 gm. of oxalic acid while stirring and then is added15.2 gm. of ammonium paramolybdate [(NH₄) ₆ Mo₇ O₂₄ .4H₂ O], 0.30 gm. ofphosphoric acid (H₃ PO₄) 85%, and 107.2 gm. of stannic chloride (SnCl₄.5H₂ O). The mixture is continually heated to maintain temperature at90°C. The length of heating time is not critical. Then 101.5 gm. of16-30 mesh pumice stone is added to the solution. The heating iscontinued until the water is evaporated then the mixture is vacuum driedand calcined in air at 450°C. for 24 hours.

EXAMPLE 2

The catalyst prepared in Example 1 is used to prepare cyanopyridines inan isothermal reactor as follows: four cubic centimeters (4 cc.) of thecatalyst prepared in Example 1 is placed into a 1/4 inch (0.635centimeter) I.D. stainless steel isothermal reactor and connected to agas chromatograph apparatus in order to analyze the feed and productcompositions of the reactor. The feed composition is adjusted to enterthe reactor as 1.1% 3-picoline, (3-methyl pyridine) 2.2% NH₃, 4.4% H₂ O(steam) and the remainder as air resulting in 27.7% oxygen (21% O₂ -79%N₂). The contact time of the reactants in the reactor is about 4.7seconds. At a temperature of about 360°C., the conversion of 3-picolineis about 45% and the selectivity to 3-cyanopyridine is about 93%. At thesame reactor conditions and feed composition with the temperature at380°C., the conversion of 3-picoline is 76% with a selectivity to the3-cyanopyridine of 90%.

EXAMPLE 3

The catalyst prepared in Example 1 is used to prepare cyanopyridines inan isothermal reactor as follows: 4 cc. of the catalyst prepared inExample 1 is placed into a 1/4 inch (0.635 centimeter) I.D. stainlesssteel isothermal reactor and connected to a gas chromatograph apparatusin order to analyze the feed and product composition of the reactor. Thefeed composition is adjusted to enter the reactor as 1.0%2-methyl-5-ethyl pyridine, 2.0% ammonia (NH₃), 3.7% steam (H₂ O) and theremainder as air giving 27.7% oxygen. The contact time of the reactantsin the reactor is about 4.7 seconds. At a temperature of about 340°C.,the conversion of 2-methyl-5-ethyl pyridine is about 22.0% and theselectivity to corresponding cyanopyridine (3-cyanopyridine) is 75.0%.

What is claimed is:
 1. A process for the production of cyanopyridinesfrom alkyl pyridines wherein the alkyl group contains 1 to 2 carbonatoms which comprises passing as a reactant stream a gaseous mixturecomprising:1. an alkyl substituted pyridine;
 2. ammonia;
 3. steam; and4. oxygenwherein the mole ratios of said reactants are: ammonia:alkylpyridine, 1:1 to 10:1; steam:alkyl pyridine, 0.01:1 to 10:1;oxygen:alkyl pyridine, 2:1 to 50:1the improvement being passing saidreactant stream over a fixed bed ammoxidation catalyst at a temperatureof about 280°C. to 400°C. and wherein said catalyst consists essentiallyof (V₂ O₅ +MoO₃ +P₂ O₅ +SnO₂)/pumice in a molar ratio of2.5:1.0:0.015:3.5 wherein the weight % loading of the catalyst on thepumice support is in the range from about 5 to 50%.
 2. A catalystcomposition consisting essentially of (V₂ O₅ +MoO₃ +P₂ O₅ +SnO₂)/pumicewherein the molar ratios of V₂ O₅ :MoO₃ :P₂ O₅ :SnO₂ are2.5:1.0:0.015:3.5 wherein the weight % loading of the catalyst on thepumice support is in the range from about 40 to 50%.
 3. The processaccording to claim 1 wherein the alkyl substituted pyridine is selectedfrom the group consisting of 2-picoline, 3-picoline, 4-picoline and2-methyl-5-ethyl pyridine.
 4. The process according to claim 1 whereinthe alkyl substituted pyridine is 3-picoline.
 5. The process accordingto claim 1 wherein the alkyl substituted pyridine is2-methyl-5-ethyl-pyridine.